If $a + b + c = -10$ and $x + y + z = -10$, what is $-6c - 6b + 6z + 6x + 6y - 6a$ ?
$= -6a - 6b - 6c + 6x + 6y + 6z$ $= (-6) \cdot (a + b + c) + (6) \cdot (x + y + z)$ $= (-6) \cdot (-10) + (6) \cdot (-10)$ $= 60 - 60$ $= 0$